Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- lock/unlock the address space of a process
int mlockall(int flags);
function shall cause all of the pages mapped by the address space of a
process to be memory-resident until unlocked or until the process exits
another process image. The
argument determines whether the pages to be locked are those currently
mapped by the address space of the process, those that are mapped
in the future, or both. The
argument is constructed from the bitwise-inclusive OR of one or more
of the following symbolic constants, defined in
Lock all of the pages currently mapped into the address space of the
Lock all of the pages that become mapped into the address space of the
process in the future, when those mappings are established.
If MCL_FUTURE is specified, and the automatic locking of future
mappings eventually causes the amount of locked memory to exceed the
amount of available physical memory or any other
implementation-defined limit, the behavior is
implementation-defined. The manner in which the implementation
informs the application of these situations is also
function shall unlock all currently mapped pages of the address space
of the process. Any pages that become mapped into the address space of
the process after a call to
shall not be locked, unless there is an intervening call to
specifying MCL_FUTURE or a subsequent call to
specifying MCL_CURRENT. If pages mapped into the address space of the
process are also mapped into the address spaces of other processes and
are locked by those processes, the locks established by the other
processes shall be unaffected by a call by this process to
Upon successful return from the
function that specifies MCL_CURRENT, all currently mapped pages of the
address space of the process shall be memory-resident and locked.
Upon return from the
function, all currently mapped pages of the address space of the process
shall be unlocked with respect to the address space of the process.
The memory residency of unlocked pages is unspecified.
Appropriate privileges are required to lock process memory with
Upon successful completion, the
function shall return a value of zero. Otherwise, no additional memory
shall be locked, and the function shall return a value of -1 and set
to indicate the error. The effect of failure of
on previously existing locks in the address space is unspecified.
If it is supported by the implementation, the
function shall always return a value of zero. Otherwise, the function
shall return a value of -1 and set
to indicate the error.
function shall fail if:
Some or all of the memory identified by the operation could not be
locked when the call was made.
argument is zero, or includes unimplemented flags.
function may fail if:
Locking all of the pages currently mapped into the address space of the
process would exceed an implementation-defined limit on the amount of
memory that the process may lock.
The calling process does not have appropriate privileges to perform
the requested operation.
The following sections are informative.
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
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